This section provides background information related to the present disclosure which is not necessarily prior art. In certain vehicles employing cell phone communications technology, code division multiple access (“CDMA”) may be a channel access method that is utilized. As part of the communication between a base station (“BS”), which is a stationary station, and a mobile station (“MS”) such as a vehicle, which is a movable station, a condition of communication overreach may be experienced. An overreach condition in a CDMA system is one in which a downlink signal from the base station can reach the mobile station (e.g. a vehicle) but the uplink signal from the mobile station cannot effectively reach the cellular base station. More specifically, as an example, FIG. 1 depicts a vehicle 10 within which a cellular communication system 12 may reside. Such a cellular communication system 12 may operate using principles of a code division multiple access (“CDMA”) protocol and further apply to a telematics system within vehicle 10. Cellular communication system 12 within vehicle 10 may utilize a voice control module 14, which may also be known as a radio unit, for establishing voice communications with remote stations, such as a base station. Cellular communication system 12 may also employ a global positioning system (“GPS”) control module 16 for receiving GPS signals for measuring the position of vehicle 10 based on reference location data sent from global, orbiting satellites, a digital control module (“DCM”) 18 for controlling the operation of voice control module 14 and GPS control module 16. A vehicle position memory 20 may be used for storing positions of the vehicle calculated and determined by GPS control module 16, and a base station position memory 22 for storing base station position information obtained by communications with base stations. Communications received by voice control module 14 and GPS control module 16 may be facilitated using respective antennas.
Turning to FIGS. 2 and 3, a known condition of overreach is depicted. More specifically, in a condition of overreach, a mobile station (“MS”) 24, which may be a vehicle 10, is located outside of (i.e. beyond or not within) a communication range 26 of a first base station (“BS1”) 28. When MS 24 is positioned as such, a communication transmission scenario depicted in FIG. 3 may occur. More specifically, BS1 28 may transmit a downlink signal 30 that is received by MS 24; however, an uplink signal 32, which may be transmitted from MS 24, never reaches BS1 28, as represented by a gap between uplink signal 32 and BS1 28 in FIG. 3. Because downlink signal 30 may be the only downlink signal received or the strongest of a multitude of signals received by MS 24, MS24 may continue to transmit an uplink signal 32 to BS1, which is never received, for a period of time that may equal a battery life of a battery 34, which may occur when vehicle engine is off and not charging battery 34. Battery 34 may also supply electricity to components within vehicle 10 other than digital control module 18, such as all other on-vehicle components, such as those that communicate with or are controlled by digital control module 18. Thus, because of ongoing communications experienced during an overreach situation, battery 34 of vehicle 10 may be completely drained of electrical energy and disable vehicle 10, including cellular communication system 12, which may be part of a telematics system.
While depleting the useful life of battery 34 is one problem of a non-received uplink signal 32, another problem is that digital control module 18 cannot provide any service, such as cellular communications as part of a telematics system during periods when MS 24 transmits an unreceived uplink signal to BS1 28, even though MS 24 may indicate that a strong downlink signal 30 is being received from BS1 28.